Assays are frequently used to detect the presence of analytes in aqueous test samples in clinical and forensic medicine, and for environmental testing, food contaminant testing, and drug use testing. There is a growing demand for such assays that are based on reactions between specifically reactive substances, and that can be conducted outside of the laboratory setting, for example at home.
There are a number of over-the-counter (“OTC”) home testing and health care professional (“HCP”) diagnostic devices that can be used to collect human body fluids and perform diagnostic assays. An example of such a diagnostic device is a dipstick used for midstream urine sampling, such as found in pregnancy testing, or testing of urine from a specimen placed in a receptacle. Both OTC and HCP diagnostic devices can be lateral flow devices, in which a liquid specimen is applied to a sample zone of a lateral flow chromatographic test strip. The strip is usually made of a porous carrier material (such as nitrocellulose) so that the liquid travels along the strip by capillary action to an indicator zone, which indicates a presence, absence, or quantity of the analyte. Sometimes a wick is attached to the strip to help move the liquid specimen into or along the sample zone. Numerous lateral flow analytical devices have been disclosed, and include those shown in U.S. Pat. Nos. 4,775,636; 4,703,017; 4,861,711; 4,855,240; 4,857,453; 4,943,522; 4,945,042; 4,496,654; 5,001,049; 5,075,078; 5,126,241; 5,451,504; 5,424,193; 5,712,172; and WO92/12428; WO 94/01775; and WO 97/06439, each of which is incorporated by reference.
Many lateral flow devices are one-step lateral flow assays in which a biological fluid is placed in a sample area on a bibulous strip, and allowed to migrate along the strip until the liquid comes into contact with a specific binding partner that interacts with an analyte in the liquid. Once the analyte interacts with the binding partner, a signal (such as a fluorescent dye) indicates that the interaction has occurred. Multiple discrete binding partners can be placed on the strip (for example in parallel lines) to detect multiple analytes in the liquid. The test strips can also incorporate control indicators, which provide a signal that the test has adequately been performed, even if a positive signal indicating the presence (or absence) of an analyte is not seen on the strip.
Although lateral flow devices have been widely used in clinical practice, there are still obstacles to both clinical and home use because of the difficulty obtaining some specimens (such as blood), or the reluctance of users to collect certain specimens (such as urine). Even in situations in which urine tests are widely used (such as urine analysis for drug testing), it can be awkward or distasteful to obtain the specimens for analysis. Moreover, it is sometimes difficult to positively identify a specimen as coming from a particular individual, because of the possibility that specimens have been mislabeled or exchanged after collection but before testing.
U.S. Pat. No. 5,910,122 (D'Angelo) discloses a saliva collector which encases a tip of an aspirating pipette, for subsequent analysis in a separate test. U.S. Pat. No. 5,380,492 shows another saliva collector which incorporates an indicator in the collector that changes color when sufficient saliva has been collected. U.S. Pat. No. 4,635,488 is a body fluid sampling device which has an absorbent nib that collects saliva and conducts it to an analysis element in an interior of a tube. The analysis element can be placed in the tube after saliva collection is completed. Alternatively, liquid communication between the nib and analysis element is altered by a porous, absorbent but hydrophobic disc that conducts the saliva to the analysis element after being wetted with a wetting agent.
A problem that has retarded the more widespread use of intra-oral collection devices is that regulatory agencies and test subjects have been concerned about the reverse migration or reflux of detection reagents from the device into the mouth. Such reflux could cause a test subject to experience a noxious taste, or even carry potentially harmful detection reagents into the mouth of the subject.
Many lateral flow tests are used for regulatory or legal purposes, and proper identification of the test subject is important. Prior devices have included a label on which identifying information can be written (for example, in U.S. Pat. No. 5,380,492). However, incorrect information can be intentionally or unintentionally entered on such labels.
It would be advantageous to provide a simple and convenient assay that is suitable for home use, avoids reflux of test reagents, and/or which can readily identify a person from whom the biological specimen is obtained.